The moon is 384,400 km or 238,900 miles from Earth and has a diameter of 3,474 km or 2159 miles. We observe the moon as just over 1/2 degree in the sky. For reference you can approximate 1 degree as the width of your index finger held at arm’s length.
Jupiter has a diameter of 139,820 km or 86,881 miles. Assuming you placed the center of Jupiter at the same distance as the center of the moon, Jupiter would take up 21 degrees of the sky. Ignoring all other effects, what you would see is a very big planet about the size of an inflatable beach ball held at arms length.
The Great Red Spot has a width of 16,350 km or 10,160 miles, almost 5 times that of the moon. Considering that the surface of Jupiter would be much closer to Earth than the moon’s surface, this would appear as 3 degrees across. The Spot alone would appear 6 times bigger than our moon.
Holy Goodness! We will be seeing a horrific, horrific sight. Depends really on what you consider “horrific” (apparently, some people don’t find horror movies horrific so yeah).
This. Except that it would be covering nearly 1/8th portion of the entire sky.
Earth would orbit Jupiter. The Moon would either get thrown totally out of orbit, or be captured by Jupiter.
Earth’s orbit around Jupiter would be 39.93 hrs at 384400 km from Jupiter’s center. The 143000 km disk of Jupiter would appear 42 times as large as the Moon now does — that is the wide-spread span of your hand from thumb tip to little finger held at arm’s length.
We would orbit nearer Jupiter than its closest large moon Io, which orbits in 42.48 hrs at an average 422000 from Jupiter’s center.
Initially, Early would still have a 24-hr day, and Jupiter would move westward 216 degrees, returning to the same position in our sky every 1.67 days.
EDIT to add information about tidal force….
The Moon/Earth mass ratio = 0.0123, while the Jupiter/Earth mass ratio = 317.8. So the force of gravity between Earth and Jupiter would be 327.8/0.0123 = 25800 times the tidal force of the Moon!
Jupiter’s tidal effect would slow Earth’s rotation down to be locked to our 40-hour orbital period, so we’d have a day about 50% longer than now.
EDT to clarify tides…
During the transition to tidal lock, there would be tremendous ocean tides that would destroy our coastlines, mountains and tectonic plates.
Once Earth rotation were locked to 40-hr orbit, there still be tidal variation due to our elliptical orbit — the same one the Moon follows now. As the distance to Jupiter varied every 40 hours, the bulges would librate (wobble) to a greater degree than the Moon does now.
Half the Earth would see the Sun only at dawn and dusk because Jupiter would block the Sun most of the day. The other half of Earth would never see Jupiter at all!
There would be strong tidal strain on Earth’s crust and mantle, for even bigger earthquakes and volcanoes than those on Io, taking away Io’s rank as #1 geologically active body in the solar system.
Jupiter’s new proximity to the Sun — 25 times more solar radiation flux — would undoubtedly have dangerous effect of adding a lot more to Jupiter’s energy, which would increase its atmospheric activity, magnetic field and its own dangerous emission of radiation from the charged materials it captures from Io’s volcanoes, plus Earth’s vastly greater volcanic output.
